1. Field of the Invention
The invention relates to a process and device for ascertaining whether two successive shafts are in alignment.
2. Description of the Related Art
Processes for exactly aligning two successive shafts to one another were carried out in the past, primarily with purely mechanical measurement means. Typical examples of activities of this type were alignment of electric motors on directly coupled pumps or comparable assemblies. Since it became possible later to replace the mechanical measurement pointers provided for in these processes by light pointers and the pertinent mechanical sensors by electronic ones, a significant facilitation and improvement in the execution of the pertinent measurement tasks were established. Simultaneous use of microprocessors in this connection, and especially for the calibration measurement to then be carried out on the corresponding machines or devices turned out to be extremely helpful.
Electronic sensors used in the form of special photoelements provided with flat resistance elements, either as selected components, or to provide a linearization process for them. In this way inaccuracies and nonlinearities relating to the location of an incident light beam, and a recordable output signal of the sensor may be kept relatively small. Furthermore, the corresponding nonlinearities were dependent on temperature to a certain extent.
The object of this invention is to largely eliminate these defects of an otherwise extremely useful older invention, especially nonlinearities, and to reduce the temperature dependency which may be present in the optical sensor/sensors to be provided, and at the same time to significantly increase the precision, i.e. the repeatability and resolution of this sensor, to a large degree.
Another object of the invention is to significantly reduce the number of optical and/or optoelectronic components to be used or to design them more economically.
These object are achieved by devising a process which is used to ascertain whether two successive shafts are in alignment with respect to their center axes or are offset against one another at an angle and/or at a distance. By means of several measurement pointers and the pertinent reference elements, a plurality of geometrical measured values can be generated via several measurement angular positions of the shafts which correspond to one another from shaft to shaft, two measurement values being independent of one another, and the measured values having a functional dependency at least on distance and angular offset (especially skewness) of the shafts. As the measurement pointer, at least one light beam in the form of a light bundle of low divergence, especially in the form of laser beam, may be used, and the light beam is oriented such that it is incident on at least one reference element in the form of an optoelectronic array with a plurality of pixels, especially a flat optoelectronic sensor which acts as a CCD (charge coupled device) and in doing so, illuminates and activates part of all the pixels of the array. The positions or coordinate values of the illuminated and activated pixels of the array are electronically determined individually, and with the aid of an electronic computer, at least one characteristic value is determined from the ascertained positions or the coordinate values which describes the location of the incident light spot on the optoelectronic array with respect to one or more coordinates.
For purposes of determining at least one characteristic value in accordance with the invention, preferably one or more, especially arithmetic averages, are computed which indicate the middle position of the light spot with respect to one or more stipulated coordinates.
In a roughly comparable manner, at least one characteristic value can also be determined by determining the focus of the light spot incident on the optoelectronic array. This focus determination relates to linear or flat arrangements of the indicated optoelectronic array. Since the light spot has no mass, it goes without saying that when the indicated focus is formed, light intensities are assumed. The light intensities can obey a continuous distribution here. But they can also be assigned to one of two intensity states, specifically to xe2x80x9con/brightxe2x80x9d or alteratively xe2x80x9coff/darkxe2x80x9d.
Furthermore, the process as claimed in the invention advantageously uses a computer and a pertinent program by which in addition to computing one or more averages the pertinent quantities, xe2x80x9cscatteringxe2x80x9d or xe2x80x9cvariancexe2x80x9d are determined. The shape of the light spot can be checked by this measure. This is based on the fact that an irregularly shaped light spot will produce other values for the indicated quantities as a light beam which is incident is regularly shaped on the optoelectronic array. In a comparable manner, if feasible, higher statistical moments can be used for evaluation and assessment of the quality of an incident light beam.
Since an incident light beam typically does not have a constant intensity over its cross section, but generally has an intensity peak in the vicinity of its axis, it is advantageous to define an edging cross sectional outline for this light beam such that before acquiring the signal, a threshold intensity is set so that activated pixels of an optoelectronic array in which the incident light beam has a local intensity greater than the aforementioned threshold intensity are considered. Therefore, this is especially advantageous because the corresponding component object can be achieved by using simple hardware in the form of a comparator. The same object can also be achieved by a suitable computer software combination, but the aforementioned approach is much more efficient and thus, economical. The required capacity of a computer which must be provided anyway, can be kept low by further processing only those pixels which can be assigned to one edge or transition between one intensity range with a first intensity value and another intensity range with a second intensity value.
To check the intensity and/or the cross sectional shape of the incident light beam, it is a good idea to check the number of activated pixels above or below stipulated boundary values. In this way, it becomes apparent whether an incident light beam is either too small or, for example, is on the edge areas of an illuminated optoelectronic array.
If enough computer time is available, it is also advantageous to supply a light spot (or its edges, as was mentioned above) to be recorded on an optoelectronic array for more extensive pattern recognition. Only when its shape recorded at the time corresponds to a stipulated criterion does optionally further evaluation take place, i.e. the determined characteristics are further used in a following computation step of a program assigned to the process in accordance with the present invention.
In another embodiment of the process in accordance with the present invention the process includes consists in another evaluation phase of recognition and computational elimination of the light portions which can be attributed to undesirable optical reflections. For this reason, in the conventional manner, methods of integral transformation, deconvolution operations and similar computer methods, especially based on the so-call Fast Fourier Transform, can be used.
In another embodiment of the invention, the process is the reverse, i.e. optical reflections are caused in a controlled manner and are used for evaluation by measurement. In this connection, it is advantageous for the provided sensor to be able to discriminate individual illuminated areas from one another and to parameterize them, i.e. to deliver the parameters for a plurality of individual objects relevant to measurement engineering. It should be remembered that to date, all devices used in this connection have been able to determine essentially only two parameters for incident light, specifically the focus of the incident light in one x-axis and in a y-axis orthogonal thereto.
Especially prompt availability of these characteristics is enabled by using the aforementioned discrimination of cases xe2x80x9con/brightxe2x80x9d and xe2x80x9coff/darkxe2x80x9d for the light intensity at the site of an individual pixel of an optoelectronic array; is also possible for more accurate analyses, if they are desired or necessary, of the locally present illumination intensity of the incident light beam to be determined for an activated pixel and to be made available as a digitized quantity for further computation processes. This approach, specifically the interconnection, for example of a CCD sensor and an analog-digital converter (ADC), is known.
Regardless of whether the latter approach is used or not, in accordance with the present invention, the location and/or the cross section (or the intensity properties over the cross section) of at least one, but preferably several light beams recorded by the optoelectronic array can be completely displayed in an extremely simple manner on a downstream display. By means of this immediate visual control possibility, a user of the process in accordance with the present invention can be immediately informed whether the number and arrangement of incident light beams of correct size, shape and location appear.
To make the process in accordance with the present invention feasible, there is a corresponding device which can have a so-called CCD sensor as an especially economical basic component. In one qualitatively improved embodiment, a so-called CMOS image sensor is used. To further improve the optoelectronic signal acquisition, it can also be feasible to make available an auxiliary device which comprises a modulation or multiplexing device using conventional art, with which the light beam can be varied in its intensity or in its beam direction, especially can be turned on and off in pulses. In particular, LCD-based modulation means are advantageous for this purpose. They can also be used to provide the light beam with a variable cross section. In this way, it is possible to even better assess the quality of the light beam incident on the optoelectronic array or to deliver it to especially high quality pattern recognition in order to achieve especially accurate determination of the aforementioned characteristics.